Embodiments of the present invention relate to RFID (Radio Frequency Identification) contactless integrated circuits which can communicate by inductive coupling or electric field coupling with other devices.
RFID integrated circuits operating by inductive coupling can be of tag type or tag reader type. FIG. 1 schematically shows a tag integrated circuit RFTG operating by inductive coupling. The integrated circuit RFTG is connected to an antenna circuit 3 and includes a modulation circuit RLM, a demodulation circuit RTD, an electric power supply circuit PMU and a processing circuit RTDU connected to the circuits RTD and RLM. The antenna circuit 3 is tuned at a resonance frequency around 13.56 MHz, and includes one or more coils AC and a tuning capacitor Cp connected in parallel to the coil AC. The antenna circuit is connected between an input of the circuits RLM, RTD and PMU and the ground Gnd of the circuit RFTG. The electric power supply circuit PMU generally includes a diode rectifier circuit to supply a power supply voltage from a voltage appearing across the antenna circuit when the integrated is subjected to an alternating magnetic field emitted by an RFID tag reader. The modulation circuit RLM generates a load modulation sub-carrier which is combined to data to be emitted provided by the processing circuit RTDU. The demodulation circuit RTD extracts from a signal received by the antenna circuit 3, data transmitted by an RFID reader, generally by modulating the amplitude of the emitted magnetic field. The circuit RTD transmits the demodulated data to the processing circuit RTDU. The processing circuit RTDU generally includes a process unit connected to volatile and non volatile memories. The tag circuit RFTG may be, for example, used in a payment or access control card, or in an identification document such as a passport or identity card.
FIG. 2 schematically shows an integrated circuit of reader RFRD operating by inductive coupling. The integrated circuit RFRD includes two terminals RX, TX connected to an antenna circuit 2, a ground terminal Gnd, an electric power supply terminal Vcc, a processing circuit RRDU, a modulation circuit RRM connected between the terminal TX and the circuit RRDU, and a demodulation circuit RRD connected between the terminal RX and the circuit RRDU. The antenna circuit 2 includes a first terminal connected to a ground terminal Gnd of the circuit RFRD, and a second terminal connected to the terminals RX and TX. The antenna circuit 2 is also tuned at the resonance frequency around 13.56 MHz, and includes one or more coils AC1 and a tuning capacitor Cp1 connected in parallel to the coil AC1. The processing circuit RRDU generally includes a process unit connected to volatile and non volatile memories and may be connected to other circuits. The reader circuit RFRD may for, example, be used in an access control reader or a payment terminal.
Recently, the Near Field Communication technology NFC has also been developed, allowing a same integrated circuit to operate in a reader mode or a card emulation mode in which the integrated circuit emulates an RFID tag which may communicate with an RFID reader or another NFC circuit. To that end, such an integrated circuit gathers the circuits RFTG and RFRD of FIGS. 1 and 2, connected to the antenna circuit 2. Thus, FIG. 3 schematically shows an NFC component, referred to as NFCC, including the circuits RFTG and RFRD. The component NFCC also includes an electric power supply terminal Vcc and a ground terminal Gnd. The antenna circuit 2 is connected to the circuits RRD, RRM, RTD, RLM and PMU. The functions performed by the processing circuits RTDU and RRDU of the circuit NFCC may be performed by a single processing circuit.
Exchanging data using the RFID or NFC technology is performed by inductive coupling between the antenna coil of a reader and the antenna coil of a tag, through an alternating magnetic field at the standardized frequency 13.56 MHz, emitted by the reader. Circuits of reader type require big antenna coils, around 12 cm2 for a reading distance around 2 cm, which is a significant constraint if the circuit is to be integrated into another system such as a mobile phone.
In addition, other contactless tag technologies exist, such as the UHF technology, based on an electric coupling between two antennas. This technology makes it possible to reach reading distances of several meters. The frequency bands used (860 to 960 MHz) by the UHF tag technology allow antennas smaller than the NFC antenna coils to be used. UHF tags generally emit data in a passive way using a retromodulation technique called “backscattering,” consisting in modulating the reflection coefficient of the antenna of the UHF tag. UHF tags may also be powered by the electric field emitted by a UHF reader. The UHF technology is mainly used in the field of traceability in production and logistics, and also to monitor items to be sold in shops.
FIG. 4 schematically shows an integrated circuit of a UHF tag, referred to as UHTG. The circuit UHTG includes a modulation circuit UBSM, a demodulation circuit UTD and an electric power supply circuit PMU, which are connected to an antenna UA1. The circuits UBSM and UTD are connected to a processing circuit UTDU.
FIG. 5 schematically shows a UHF reader circuit, referred to as UHRD. The circuit UHRD includes a modulation circuit URM and a demodulation circuit URD. The circuit URM is connected by a terminal TX to an antenna UA2, possibly through an amplification circuit PA. The circuit URD is connected by a terminal RX to the antenna through a band-pass filter BPF. The circuit UHRD is powered between terminals Vcc and Gnd.
In International Patent Publication No. WO 2004/034317 (also published as US Patent Publication No. 2005/0186904), it has been suggested to combine circuits operating by inductive coupling and electric coupling in a same tag circuit. FIG. 6 schematically shows a tag circuit, referred to as RUTG. The tag circuit RUTG is connected to a UHF antenna UA1 and an HF antenna circuit 3. The circuit RUTG includes HF modulation and demodulation circuits RLM, RTD connected to the antenna circuit 3, UHF modulation and demodulation circuits UBSM, UTD connected to the antenna UAL and a processing circuit RUDU connected to the modulation circuits RLM, UBSM and the demodulation circuits RTD, UTD. The circuit RUTG also includes an electric power supply circuit PMU1 connected to the antenna UA1 and the antenna circuit 3.
There is a need for devices combining NFC and UHF technologies, in particular to offer new applications thanks to the longer range provided by the UHF technology. However, integrating into a same component HF and UHF modulation and demodulation circuits leads to a component having relatively significant dimensions. There is therefore a need to decrease the dimensions of such a component.